Constructing ranges

I seem to have hit a wall with regard to constructing ranges. It appeared to be going well for a while but now I'm second guessing a lot.

When figuring out a range where do you account for bluffs?

say on the flop a guy check raises you. Logically it polarises his hand into strong or bluff. But at that point should you disregard the complete bluffs carry on with the logical hands that would check raise and then attach something like a bluff/air factor to that particular player or just keep in all the trash that he knows can only win with a bluff. Or just forget about the complete blufgas.

To start with I just took logical steps forward in constructing a range but now when I'm taking out all the kx that aren't paired, AK, KQ or clubs on a board like Ac Js 3c I start to think "well if he has those hands and decides he want to win the pot he could float or check raise"